Valves

ABSTRACT

The invention relates to valves and particularly, though not exclusively, to gate valves. There is provided a valve comprising a housing ( 1 ) and a valve member ( 2 ) moveable within the housing ( 1 ) to open and close the valve. In a first aspect the valve is provided with means to reduce friction between the housing ( 1 ) and valve member ( 2 ). In a second aspect the valve is provided with an operating member ( 20 ) which is associated with the valve member ( 2 ) and passes through an aperture ( 21 ) in the housing ( 1 ) which is sealed when the valve is in the open position. Such a valve addresses difficulties relating to the operation of prior art valves, particularly gate valves, and specifically the difficulties created by frictional drag upon movement of the valve member, and difficulties in maintaining the valve.

The invention relates to valves and particularly, though notexclusively, to gate valves.

A typical gate valve comprises a valve housing and an obturator movablein the housing between open and closed positions.

When the valve is closed or partly closed, the pressure is greater onone side of the obturator than on the other. This unbalanced pressurecreates a force pushing the obturator against supporting surfaces in thehousing.

When the valve is operated, this force creates a friction drag whichresists movement of the valve member. The force required to operate thevalve is proportional to the friction drag.

It is beneficial to reduce the operating force for both hand operatedand power operated valves. The equipment for the power operation ofvalves is generally sold in a range of fixed sizes. If the operatingforce can be reduced sufficiently, it becomes possible to use a lowerpowered, lower cost operating device.

It is an object of a first aspect of the invention to provide aneffective low cost method of substantially reducing the force requiredto operate valves,

According to a first aspect of the invention, there is provided a valvecomprising a valve housing, a valve member slidable in the valve housingbetween open and closed positions, and means to reduce friction betweenthe valve member and the valve housing.

Preferably, low friction slide surfaces are provided on the obturator ofa gate valve.

Preferably, the obturator is encapsulated in or made from elastomericmaterial to provide resistance to corrosion, the low friction slidingsurfaces being provided externally of the elastomeric material.

It is generally desirable to have elastomeric material to providecorrosion protection but elastomeric material generally has a highcoefficient of friction resulting in high friction drag and highoperating forces.

By providing low friction sliding surfaces externally of the elastomericmaterial, the corrosion resistance of the obturator is retained, whilereducing the force required to operate the valve.

The low friction sliding surfaces may be provided by at least one guideshoe made of low friction material, and attachable to the obturator.

Preferably there are two guide shoes, provided at opposite edges of theobturator.

Each shoe is preferably attachable to the obturator by inserting theshoe into a slot in the obturator.

Preferably, each slot is closed at its upper and lower ends, trappingthe guide shoe within the slot such that vertical movement of the guideshoe with respect to the obturator is substantially prevented.

Each guide shoe may be a press fit in the associated slot.

Each guide shoe may be provided with ridges which dig into theelastomeric material of the obturator to help retain the guide shoe inthe associated slot.

The housing may be provided with parallel guide ribs extending down eachside of the housing, these ribs cooperating with parallel guide channelsin the guide shoes, so that the obturator is guided by cooperation ofthe ribs and channels, as the obturator moves between the open andclosed positions.

The ribs on the valve housing may be of metal or of metal provided witha corrosion protected coating. The cross section of the guide ribs ispreferably rectangular, although other shapes may be used.

The ridges on the guide shoes may be of saw tooth cross-section to makeit relatively easy to insert each guide shoe into the associated slot,but relatively hard for the shoe subsequently to move out of the slotagain.

The inner surfaces of each guide shoe fit around the associated guiderib of the housing, with a sufficient clearance to allow sliding motionto take place.

The back of each guide shoe may be shaped to fit into a recess withinthe associated guide slot of the obturator. For example each guide shoemay be provided with a central rib extending along its length from theback of the shoe.

Many other shapes are however possible. This prevents each guide shoefrom sliding out of the associated guide slot parallel to the directionof valve operation.

Each recess may be coated with elastomeric material although this is notessential.

Embodiments of the invention have the following advantages.

A device is provided for reducing the operating force in a gate valve.

The device is made from low friction material.

The device may be made from plastics material.

Acetal plastics may be used.

The device may be used with an obturator encapsulated in or made fromelastomeric material.

The device may consist of at least one channel cooperating with at leastone guide rib on the housing or any part of the valve.

The device may be retained in the obturator by means of an interferencefit with elastomeric material.

The device may have ridges on its surface in contact with theelastomeric material.

The ridges may be shaped so that the device may be inserted more easilythan it can be withdrawn.

The device may be arranged to cooperate with a recess in the obturatorso that it cannot be extracted from the obturator in the direction ofobturator motion.

According to a second aspect of the invention, there is provided a valvecomprising a valve housing, a valve member slidable in the valve housingbetween open and closed positions, a valve operating member associatedwith the valve member and passing out of the valve housing through anaperture, the valve having means to seal the aperture when the valvemember is in the open position.

The sealing means may comprise an auxiliary seal on the valve memberwhich comes into sealing contact with both the valve housing and thevalve operating member when the valve member is in the open position.

Alternatively, there may be an auxiliary seal on the valve housing whichis contacted by the valve member when the valve member is in the openposition.

Another possibility is that there may be a first auxiliary seal on thevalve member and a second auxiliary seal on the valve housing, the twoauxiliary seals coming into sealing contact with one another and withthe valve operating member when the valve member is in the openposition.

Preferably there is a main seal to provide sealing contact between thevalve operating member and the aperture.

When it is desired to replace or repair the main seal, the valve membermay be moved into the open position, in which the auxiliary seal sealsthe aperture while the main seal is being replaced or repaired.

The invention includes a valve having the features of both the first andsecond aspects of the invention.

By way of example, specific embodiments of the invention will now bedescribed, with reference to the accompanying drawings in which:

FIG. 1 is a cross sectional view of an embodiment of valve according tothe invention, taken on the centre line of the valve;

FIG. 2 is a cross-sectional view, to a larger scale, through a guideshoe of the valve shown in FIG. 1;

FIG. 3 is a part cross-sectional view through an obturator of the valve,taken in the plane of the obturator;

FIG. 4 is a side view of the obturator shown in FIG. 3;

FIG. 5 is a cross-sectional view through a second embodiment of valveaccording to the invention, looking in the direction of flow;

FIG. 6 is a view of the obturator of the valve shown in FIG. 5; and

FIG. 7 is a detailed view of part of the obturator shown in FIG. 6.

The valves shown in FIGS. 1 to 4 has a valve housing 1 and a gate orobturator 2 moveable down into the housing 1 to close the valve, andmovable back up again to open the valve.

The obturator 2 comprises a metal casting 3 encapsulated in anelastomeric substance 4.

At each vertical edge of the obturator there Is a slot 15 having arecessed portion 16. The recessed portion 16 is closed at its upper 17and lower 18 ends.

Plugged into each slot 15 is a guide shoe having the cross section shownin

FIG. 2. A central rib 12 at the rear of each guide shoe engages in theassociated recess 16 and longitudinal ridges 13, 14 dig into theelastomeric material at the sides of the associated slot 15. Thisdigging in tends to retain each guide shoe in its associated slot in thehorizontal direction and the guide shoe cannot move out of the slot inthe vertical direction because of the engagement of the upper and lowerends of the rib 12 with the upper 17 and lower 18 ends of the recessedportion 16 of the associated slot 15.

The housing 1 is provided with oppositely facing guide ribs 5 and 6 and,as best seen in FIG. 1, these cooperate with the channels in the guideshoes 7 and 8 to guide the obturator between its open and closedpositions. Each rib projects between side arms 9 and 10 of theassociated guide shoe, and the inner face of each guide rib is closelyadjacent to the inner face 11 of the associated guide shoe channel.

Because of the inter-position of the guide shoes between the valvehousing 1 and the obturator 2, the obturator 2 can still be encased incorrosion resistant material, which usually has a high coefficient offriction. This does not mean that more power is required to operate thevalve because the only contact between the valve housing and the valveobturator is via the low coefficient of friction guide shoes 7 and 8.

The valve shown in FIG. 5 operates in a generally similar manner to thatshown in FIG. 1, having a valve housing 1 and an obturator 2. Theobturator 2 moves up or down to open or close the valve as desired.

The obturator 2 is operated by a valve stem 20 which passes out of thehousing 1 through an aperture 21. A main seal 22 is provided to reducethe possibility of fluid leaking out of the valve housing around thevalve stem 20.

In many circumstances it may be necessary to replace or repair the mainseal 22, without taking the valve out of service.

To facilitate this, the upper part of the obturator 2 is provided withan annular auxiliary sealing member 23 which is shown in more detail inFIG. 7. There is an annular metal casting 24 surrounded by elastomericmaterial 25. The elastomeric material 25 has a protruding annular rib26.

If it is decided to provide an auxiliary seal around the valve stem 20,while the seal 22 is replaced or repaired, the obturator is raised intothe fully open position. In this position, the protruding annular rib 26is compressed upon the underside 27 of the upper part of the valvehousing 1. This compression causes the elastomeric material 25 to becompressed radially inwardly to seal against the valve stem 20.

Instead of providing an auxiliary seal on the obturator, the auxiliaryseal could be provided on the underside 27 of the valve housing 1, oralternatively there could be two auxiliary seals, one on the obturatorand one on the housing, which are compressed against one another andagainst the stem 20 when the valve member moves into the open position.

The valve shown in FIGS. 1 to 4 may be provided with an auxiliary sealas shown in FIGS. 5 to 7.

The readers attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings), may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extend to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1-22. (canceled)
 23. A valve comprising a valve housing, a valve memberslidable in the valve housing between open and closed positions, andmeans to reduce friction between the valve member and the valve housing.24. A valve according to claim 23 wherein the valve comprises a gatevalve and the slidable member comprises an obturator with low frictionslide surfaces.
 25. A valve according to claim 24 wherein the obturatoris encapsulated in or made from elastomeric material to provideresistance to corrosion, the low friction sliding surfaces beingprovided externally of the elastomeric material.
 26. A valve accordingto claim 24 wherein the low friction sliding surfaces are provided by atleast one guide shoe made of low friction material, and attachable tothe obturator.
 27. A valve according to claim 26 wherein there are twoguide shoes, provided at opposite edges of the obturator.
 28. A valveaccording to claim 26 wherein the or each guide shoe is attachable tothe obturator by inserting the shoes into a slot in the obturator.
 29. Avalve according to claim 28 wherein the or each guide shoe is arrangedto cooperate with the slot in the obturator so that it cannot beextracted from the obturator in the direction of obturator motion.
 30. Avalve according to claim 28 wherein the or each guide shoe is providedwith ridges arranged to contact the elastomeric material of theobturator to help retain the guide shoe in the associated slot.
 31. Avalve according to claim 30 wherein the ridges on the or each guide shoeare shaped to make it relatively easy to insert the guide shoe into theassociated slot, but relatively hard for the shoe subsequently to moveout of the slot again.
 32. A valve according to claim 27 wherein thehousing is provided with parallel guide ribs extending down each side ofthe housing, these ribs cooperating with parallel guide channels in theguide shoes, so that the obturator is guided by cooperation of the ribsand channels, as the obturator moves between the open and closedpositions.
 33. A valve according to claim 32 wherein the ribs on thevalve housing comprise metal or metal provided with a corrosionprotected coating.
 34. A valve according to claim 32 wherein the innersurfaces of each guide shoe fit around the associated guide rib of thehousing, with a sufficient clearance to allow sliding motion to takeplace.
 35. A valve according to claim 28 wherein the back of the or eachguide shoe may be shaped to fit into a recess within the associatedguide slot of the obturator.
 36. A valve according to claim 23 whereinthe valve comprises a valve operating member associated with the valvemember and passing out of the valve housing through an aperture, thevalve having means to seal the aperture when the valve member is in theopen position.
 37. A valve comprising: a valve housing having aninterior surface on an underside of the house; a valve member slidablein the valve housing between open and closed positions: a valveoperating member associated with the valve member and passing out of thevalve housing through an aperture; seal means for sealing the aperturewhen the valve member is in the open position, and low friction slidingsurfaces provided by at least one guide shoe made of low frictionmaterial and attachable to the slidable valve member.